Systems and methods for treating tissue are disclosed. The target tissue is ablated. A real-time image of the target tissue is generated during the ablation. The real-time blood perfusion level of the target tissue is determined from the real-time image and compared to an initial blood perfusion level of the target tissue. The comparison provides a metric for the progress of the ablation, and ablation is halted when the real-time blood perfusion drops below a threshold level relative to the initial blood perfusion level.